#include <stdio.h>
int fib(int n)
{
    if (n == 2 || n == 1)
        return 1;
    else
        return fib(n - 1) + fib(n - 2);
}
int main()
{
    int n;
    scanf("%d", &n);
    printf("%d", fib(n));
    return 0;
}